1. Field of the Invention
The present invention relates to an LED lighting unit for a vehicle. More particularly to an LED lighting unit for a vehicle wherein a light emitting diode as a light source and a board for the lighting unit can be cooled efficiently.
2. Description of Background Art
A lighting unit for a motorcycle wherein a light emitting diode (LED) is used as a light source is conventionally known. The LED is small in size in comparison with an incandescent bulb to enable miniaturization of a lighting unit. However, since the LED is an electronic part mounted on the surface of an electronic board and the degree of importance of thermal management rises together with an increase in the amount of light from the LED, a different scheme from that for an incandescent bulb may be required for the arrangement structure of the LED.
Japanese Patent Laid-Open No. 2008-192313 discloses an LED lighting unit that has two kinds of reflectors for a low beam and a high beam and wherein changeover between a low beam and a high beam is carried out by changing the irradiation direction of the LED using an actuator. In this lighting unit, a heat sink as a cooling mechanism is provided at a side portion of an LED board which is pivotally moved by the actuator.
Japanese Patent Laid-Open No. 2004-342574 discloses another LED lighting unit for a vehicle wherein a board on which an LED for a low beam is mounted and a board on which another LED for a high beam is mounted are disposed in a spaced relationship from each other such that LED mounting faces for the LEDs are directed in upward and downward directions.
According to the LED lighting unit disclosed in Japanese Patent Laid-Open No. 2004-342574, a low beam and a high beam can be provided by a simple structure without using such an actuator as in Japanese Patent Laid-Open No. 2008-192313. However, such a cooling mechanism as the heat sink disclosed in Japanese Patent Laid-Open No. 2008-192313 is not provided. Thus, there is room for improvement in thermal management.
On the other hand, where the shape and the disposition of the heat sink disclosed in Japanese Patent Laid-Open No. 2008-192313 are applied, it is difficult to assure a great capacity. Further, since the heat sink can be visually recognized from outside the lighting unit, the appearance of the lighting unit is deteriorated.